为什么 CTRL-D 信号没有使用此程序进行 EOF？[复制]

问：

当我运行这个程序时，我输入一个IP地址和服务器端口作为输入。但是，在此之后，程序要求我“请输入msg：”。但是，在键入我的消息后，按 ctrl-D 不会执行任何操作。程序仍从 STDIN 读取。如何指示我正在输入的消息的结尾？

这是我正在使用的程序：

/* 
 * echoclient.c - A simple connection-based client
 * usage: echoclient <host> <port>
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h> 

#define BUFSIZE 1024

/* 
 * error - wrapper for perror
 */
void error(char *msg) {
    perror(msg);
    exit(0);
}

int main(int argc, char **argv) {
    int sockfd, portno, n;
    struct sockaddr_in serveraddr;
    struct hostent *server;
    char *hostname;
    char buf[BUFSIZE];

    /* check command line arguments */
    if (argc != 3) {
       fprintf(stderr,"usage: %s <hostname> <port>\n", argv[0]);
       exit(0);
    }
    hostname = argv[1];
    portno = atoi(argv[2]);

    /* socket: create the socket */
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) 
        error("ERROR opening socket");

    /* gethostbyname: get the server's DNS entry */
    server = gethostbyname(hostname);
    if (server == NULL) {
        fprintf(stderr,"ERROR, no such host as %s\n", hostname);
        exit(0);
    }

    /* build the server's Internet address */
    bzero((char *) &serveraddr, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
    bcopy((char *)server->h_addr, 
      (char *)&serveraddr.sin_addr.s_addr, server->h_length);
    serveraddr.sin_port = htons(portno);

    /* connect: create a connection with the server */
    if (connect(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0) 
      error("ERROR connecting");

    /* get message line from the user */
    printf("Please enter msg: ");
    bzero(buf, BUFSIZE);
    fgets(buf, BUFSIZE, stdin);


    /* write: send the message line to the server */
    n = write(sockfd, buf, strlen(buf));
    if (n < 0) 
      error("ERROR writing to socket");

    /* read: print the server's reply */
    bzero(buf, BUFSIZE);
    n = read(sockfd, buf, BUFSIZE);
    if (n < 0) 
      error("ERROR reading from socket");
    printf("Echo from server: %s", buf);
    close(sockfd);
    return 0;
}